Braun tube



March 30, 1937. K, SCHLESlNGER 2,075,142

BRAUN TUBE Filed om. 18, 1935 MQW@ Patented Mar. 30, 1937 UNITED sTATEsPATENT OFFICE Application October 18, 1933, Serial No. 694,135 InGermany October 21, 1932 4 Claims.

Heretofore it has been assumed that the delecting potentials necessaryfor acting on the image screens of Braun tubes are dependent insubstance on the arrangement and embodiment 5 of the deecting plates,and that by increasing the deflecting potential an improved effect maybe obtained.

The applicant has found that the potential necessary for the operationof Braun tubes is determined solely by the dimensions of the bulb of thetube and by the anode potential. This optimum potential-upon an increaseof which an improved effect does not take place-may be calculatedaccording to the formula E17=}/2Ea' wherein Ep is the plate deiiectionpotential, Ea the anode potential, D the diameter of the image 20screen, and L the length of the tube.

For a tube of 30 cm.` in length and 20 cm. in diameter of the imagescreen there results with an Ea of 1500 volts;

2 2 Ev=%.1500g= approximately 335 volts According to the invention, theplate deflection potentials should be provided with values approximatelyagreeing with those resulting from the above formula, and should in noway exceed the same to an appreciable extent.

Television images produced with the known Braun tubes do not possess therequisite rectangular form, but are rather more of a substantiallytrapezoidal shape disclosing corresponding distortions of the contentsof the picture in a horizontal direction.

The applicant has ascertained that these disturbances are caused bymarginal eld eiects of the pairs of deilecting plates on each other, andthat it is possible by suitable arrangement and dimensioning of theplates to preclude this disturbing effect and to produce completelyrectangular images.

'Ihe strength and accordingly the influence of the marginal elds isdetermined by the ratio between the spacing of the plates of the singlepairs and the spacing between the pairs of plates themselves,

According to the invention, the ratio between the spacing of the pairsof plates in relation to each other and the spacing of the platesthemselves is selected to be equal to or greater than 3 (the essentialfeature in this connection is the (Cl. Z50-27.5)

spacing at the rear end of the front deflecting plates).

In order now to permit of a construction of the system as compact aspossible it is desirable in accordance with the invention to provide the5 deilecting plates with a certain tilt in relation to each other.. Inthis connectionparticularly if the plates are relatively short (forexample l5 mm.)-the one plate may be arranged parallel to the axis, andthe other plate furnished with l0 a certain inclination in relation tothe first plate, whereby a considerable simplification in the con-vstruction of the system is obtained.

This arrangement is particularly suitable in connection with tubes witha so-called bending 15 of the ray, i. e., in the case of tubes in whichbetween the anode and the first pair of deflecting plates there isprovided a deflecting element imparting a constant preliminarydeflection 'to the cathode ray. In this case the tilt of the one 20deilecting plate of both systems in relation to thesecond plate parallelto the axis may be selected in such fashion that the preliminarilydeflected ray enters the deflecting systems lapproximately parallel tothe tilted plate. 25

It has been found to be convenient to employ plates of approximately 15mm. in length, and to select the spacing of the front edges of theplates at approximately 5 mm. and that of the rear edges of the platesat approximately 1.5-2 mm. 30

A particular advantage of this arrangement resides in the fact that itis possible by altering the inclination of the plates to vary thesensitiveness (i. e., the movement in mm. per volt of de- 35 ectingpotential) within wide limits, without varying at the same time the sizeof the image.

The invention is illustrated by way of example in the drawing,

Fig. 1 of which shows the neck portion of a 40 Braun tube according tothe invention, incorporating the electrode system, whereas Fig. 2 showsthe conically enlarged portion of the tube and should be read as theright hand continuation of Fig. 1. 45

In the drawing, I is the wall of the tube, 2 the Wehnelt cylinder, whichis secured to the holder 3 and within which there is arranged thecathode 4, 5 a preliminary anode, 6 a concentration cylinder and 1 theafter-acceleration anode. 8 is 50 the deflecting element, which iscomposed of two angle plates 2,0 and 2|, and which imparts to the ray aconstant preliminary deection. The plate 20 of this element isconductively connected with the anode, whilst the plate 2l receives inrelation to the plate 20 a constant bias from the battery I 6. 9 and I 2are the two pairs of deflecting plates. 'I'he plates I0 and I3 arelinked up with the same potential as the plate 2 I, whilst the plates II and I 4 receive the deecting potentials from the lgenerators I8 andI9. The plates I0 and I3 are disposed parallel to the axis, whilst theplates II and I4 are tilted in relation to the axis-which is so chosenthat the lpreliminarily deflected ray enters the system approximatelyparallel to this plate. Since the plates I0 and I3 possess a stronglypositive bias-which conveniently mayV be.-

greater than the maximum deflection amplitude occurring-the totalso-called cross-current will be attracted towards these plates, whilstthe actual control plates II and I4 remain absolutely free ofcross-current- Y The tube according to the invention is devoid of crossand cross-current defect, and permits of the production of imagescompletely free of distortion with the smallest application ofpotential.

I claim:

l;v A Braun tube for television purposes which comprises an evacuatedenvelope, a cathode and an anode arranged in operative relationshipthereto, a Wehnelt cylinder surrounding said cathode, a picturereceiving screen, one pair of deflecting plates arranged between saidanode and said screen, andra further pair of deilecting plates arrangedbetween the first said pair and the screen, said two pairs facing oneanother, characterized in thatat least the plates ofthe further saidpair of deflecting plates are inclined with respect to one another andthat the distance between .said two pairs of Vdeflecting plates is atleast three times `as great as the distance between the plates of thefurthersaid pair at the end facing said anode.

2. A Braun tube for television purposes which comprises an evacuatedenvelope, a cathode and an anode arranged in operative relationshipthereto, a Wehnelt cylinder surrounding said cathode, a picturereceiving screen, one pair of deflecting plates arranged between saidanode 2,075,142 i y and said screen, and a further pair of deecting'platesy arranged between the rst said pair and the screen, said twopairs facing one another, characterized in that means are arrangedbetween said anode and the first said pair of deecting plates forimparting a constant deection to the ray in two directions,perpendicular to one another, that at least the plates of the furthersaid pair of Y deflecting plates are inclined with yrespect to oneanother, and that the distance between said two pairs ofdeflectingplates is at least three Vtimes as great as the distance between theplates of the further said pair of deecting plates at the end facing theanode. k

3. A Braun tube for television purposes which comprises an evacuatedenvelope, a cathode and an anode, arranged in operative relationshipthereto, a Wehnelt cylinder surrounding said cathode, a picturereceiving screen, and two pairs of deflecting plates arranged betweensaid anode and said screen, said two pairs facing one another,characterized in that the plates of at least one pair of deflectingplates have a length of approximately 15 mm. and a distance of at least1.5 mm. from one another at their ends facing the anode, and a distanceof at least 4 mm. from one another at their ends facing the screen, andthat the distance between said two pairs of deflecting plates is atleast three times as great as the distance between the plates of. thepair of deflecting platesrwhich is arranged next to said screen atrtheend facing said anode.

fl. A Braun ktube for television purposes whic comprises an evacuatedenvelope, a cathode and an anode arranged in operative relationshipthereto, a Wehnelt `cylinder surrounding said cathode, a picturereceiving screen and two pairs of'deflectin-g platescmounted in axial'consecution to each other without any further element being disposedtherebetween, characterized in that the distance between said pairs ofdeflecting plates is at least three times as great as the distancebetween the two plates of eachrof said pairs of deflecting plates.

KURT SCHLESINGER.

